InSilc Degradation Module
Compared to permanent BMSs, the design of the next-generation of drug-eluting BVS is complicated by the range of interacting physiochemical parameters that control material degradation in both polymer- and metal-based devices. In the case of synthetic polymers, bulk degradation takes place through a two-phase autocatalytic process, initiated by chemical hydrolysis of the polymer chains, which alters the pH in the local environment, in-turn accelerating the rate of hydrolytic breakdown of the polymer Degradation in metal-based devices generally takes place through an electrochemical process, whereby the alloying elements and an electrolyte form a galvanic cell, which results in heavily localised surface-based pitting corrosion adjacent to the cathode. Capturing the effects of the in vivo environment on bulk- or surface-based degradation mechanisms of polymer and metal-based bioresorbable materials through computational simulation presents significant challenges. The current state-of-the-art in degradation modelling of drug-eluting BVS has largely used phenomenological models to capture material behaviour. In the case of polymer-based degradation, continuum damage mechanics approaches have been developed that capture the effect of polymer chain scission through a degradation damage variable, that operates on materials parameters of the chosen constitutive law. Similarly, metal-based corrosion has been captured through the use of continuum damage mechanics, whereby a corrosion kinetic parameter controls the load-bearing capacity of surface elements.